This invention relates to polyolefinic polymers having improved properties. In particular this invention relates to reducing the blocking properties of polyolefinic compositions. An important aspect of this invention is a polyolefinic composition containing lactamides having saturated substituents.
Olefin homopolymers and copolymers are of commercial importance for the manufacture of numerous articles such as films and other items. In order to be useful for many of these functions it is desirable that the polyolefinic composition have good slip characteristics. This can be determined by measuring the coefficient of friction of the polyolefin. It is also important that the polyolefinic composition have good antiblock property.
In order to obtain a satisfactorily low block, often antiblock agents are added to the polyolefin to lower its blocking characteristic. Many antiblock agents and other additives for polyolefins are disclosed in the literature. These additives will lower the blocking force of the polyolefin to desired levels, permitting ready handling of shaped articles and films prepared from the polyolefinic material. Polyolefinic polymers having poor slip and poor antiblock characteristics are difficult to handle when the polymer is manufactured in the customary manner of large rolls. During storage and subsequent processing, the low slip and high block films tend to adhere layer to layer. Also such films can encounter large frictional forces in processing equipment that often cause distortions and even tearing of the film, especially when using thin film.
Rowland et al U.S. Pat. No. 2,956,979 discloses inhibiting the blocking tendencies of polyethylene by introducing into the composition a small amount of an alkylol amide of the structural formula: ##STR2## wherein R is a saturated aliphatic acyl radical of from about 18 to about 30 carbon atoms and R' is an alkyl radical group of 1 to 6 carbon atoms. Toy et al U.S. Pat. No. 3,028,355 discloses the use of diatomaceous earth to reduce the tendency of polyethylene to block. Haeske et al U.S. Pat. No. 3,266,924 discloses the blending of a mixture of finely divided siliceous material and a fatty acid amide slip agent into polyethylene to enhance its slip and antiblocking properties. Ross et al U.S. Pat. No. 3,326,840 discloses the incorporation of a small amount of a mono-N-substituted saturated carboxylic acid amide of the formula: ##STR3## wherein R is an aliphatic acyl radical having from 12 to 30 carbon atoms and R' is an aliphatic group having from 1 to 6 carbon atoms, especially an alkylol group, into a copolymer of ethylene and an aliphatic ethylenically unsaturated carboxylic ester to improve its resistance to blocking and improve its slip properties.
Foster U.S. Pat. No. 3,647,738 discloses blending an amide having the formula: ##STR4## wherein R is an alkenyl radical having 18 to about 22 carbon atoms and R' is a divalent hydrocarbon radical containing 3 to 15 carbon atoms with an alpha-olefin polymer composition to provide compositions having low blocking and no bloom characteristics and high slip properties.
The foregoing patents and other literature disclose a variety of additives that improve the slip and/or blocking properties of polyolefins. It is important that the polyolefinic compositions containing the agents have reduced blocking properties so that films and other products made from the polyolefin can be stacked or otherwise piled together.
Accordingly it is an object of the present invention to reduce the blocking properties of polyolefins.
Also an object of the present invention is the prevention of polyolefin films from adhering to each other during storage.
Another object of the present invention is to reduce the blocking to polyolefin compositions without adversely affecting the optical properties of the polyolefin.
Other objects of the present invention will become apparent from the ensuing description.